It is known to incorporate precipitated silicas into rubber mixtures (S. Wolff, Kautschuk und Gummikunstst. 7 (1988) p. 674). For use in rubber mixtures, precipitated silicas must be readily dispersible. A poor dispersibility is often the reason why precipitated silicas are not employed in tire mixtures, especially with high filler contents.
The document EP-A 0 520 862 discloses precipitated silicas which are employed as a filler in rubber mixtures for tires.
The document EP-A 0 157 703 discloses a precipitated silica which can be prepared in accordance with the document EP-A 0 501 227.
The known precipitated silicas have the disadvantage that they have a poor dispersion.
EP-A 0 647 591 and EP-A 0 157 703 describe a precipitated silica which has an improved dispersion compared with the above mentioned precipitated silicas. Due to increased requirements by the tire industry, even the improved dispersion of this precipitated silica is no longer adequate for use in tire mixtures.